1.Position a rack in the center of the oven and preheat to 325F.,Lightly butter the bottom and sides of a 12-inch diameter pizza pan.,2.Melt the unsweetened chocolate according to the melting instructions inthe Chocolate Melting Tips.,Cool until the chocolate is tepid.,3.,Chop the bittersweet and milk chocolates into 1/2-inch squares and set aside.,In a small bowl, using a wire whisk, stir together the flour and salt.,4.In a large bowl, using a hand-held electric mixer set at medium speed, beat the butter and brown sugar for 1 to 2 minutes, until the mixture is light in texture and beige in color.,One at a time, beat in the eggs, mixing well after each addition.,Beat in the melted chocolate and vanilla until blended.,At low speed, beat in the flour mixture just until combined.,5.,______,Scrape the batter into the prepared pan and using a spatula, evenly smooth the surface.,Sprinkle the surface with the remaining chopped chocolate pieces and pecans.,6.Bake for 25 to 30 minutes, or until a cake tester or toothpick inserted 2-inches away from the center comes out clean.,Transfer the pan to a wire rack to cool.,7.Melt the white chocolate according to the melting instructions in the Chocolate Melting Tips.,Fill a small paper cone with the melted white chocolate and cut a 1/3-inch opening at the tip.,Drizzle the white chocolate over the surface of the pan.,Cut into wedges to serve.